There are two parts to the setup of a display:
1) you need to describe the connectivity, these are the changes you have already made to the device tree to get the SN65DSI83 somewhat working.
2) You also need to describe the timing information, this is dependent upon the panel you have connected. In general every panel is different, hence you will need to look at the datasheet for the specific panel you have selected. Take a look at Documentation/devicetree/bindings/display/panel/display-timing.txt for more info.
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